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Chihuahua Medical Care

Treatment of 'Killer' for Epilepsy

Mrs Bate-de-Zylva sent us this information to share with you re
her dog 'Killer', seven and half year old chihuahua.

Killer was examined on the 30.10.2002 for
investigation of a recent onset of epileptic seizures. A first
suspected epileptic seizure was observed at the end of August 2002.
Ten days later, Killer developed status epilepticus. The last
epileptic seizure was witnessed since this status epilepticus.
Killer is currently on the following anti-convulsant: Phenobarbitone
elixir 0.5 ml (1.5 mg) twice daily and Sodium Valproate 50 mg three
times daily as well as Metacam 3 drops once daily and Maxitrol twice
daily.

Neurological examination: Revealed normal mental
status, posture and gait. Postural reactions were normal on all four
limbs. Spinal reflexes were normal on all four limbs. Cranial nerves
examination was normal. Cutaneous trunci reflex was normal. No
hyperaesthesia could be detected on palpation of the spine.

MRI scan of the brain and CSF analysis were performed on the
30.10.2002. MRI scan of the brain only revealed moderate
hydrocephalus and a small quadrigeminal cyst. CSF was collected
by lumbar puncture. Results are pending and will be forwarded to
you soon.

At this stage, pre-referral blood analysis ruled out metabolic
encephalopathy. The only structural abnormality detected on MRI scan
of the brain is a moderate hydrocephalus. Pending CSF analysis
results should help us to rule out inflammatory/infectious CNS
diseases. In case of normal results, the more likely diagnosis
would be primary (or idiopathic) epilepsy. The hydrocephalus and
quadrigeminal cyst are likely to he congenital considering the breed
as well as the persistent fontanel and appear therefore as less
likely causes for the epileptic seizures. The diagnosis of primary
(or idiopathic) epilepsy is unfortunately a diagnosis of exclusion
after elimination of extra-cranial metabolic causes and intra-cranial
structural causes. There is no definitive diagnostic test for this
condition.

Treatment: The treatment of primary epilepsy is only
symptomatic and consists in administration of anti-convulsant
medications (Phenobarbitone and/or Bromide). The aim of this
symptomatic treatment is to reduce the frequency, intensity and
severity of the seizures with acceptable side effects.

As discussed on the telephone, 1 will suggest continuing Killer on
Phenobarbitone elixir 0.5 ml, (1.5 mg) twice daily and Sodium
Valproate 50 mg three times daily. 1 will also suggest doing serum
Phenobarbitone level at the end of this week to ensure that therapeutic
serum concentration has been reached. Oral dosage of phenobarbitone
will need to be adjusted depending on this serum level. Do not hesitate
to contact me if you need any advice doing this oral dosage adjustment.
I will finally suggest slowly taking Killer off the valproate acid
(over a four to five days period), when serum Phenobarbitone level has
been reached.

Phenobarbitone is known to be hepatic enzyme inducer (Cytochrome P450)
which means that serum level tends to drop with time.

Therapeutic monitoring of serum drug concentration can be helpful in
determining the optimal dose. This is indicated when steady state
blood levels are reached after starting treatment (10 to 15 days) or
changing dose. This provides a baseline to guide further changes in
doses according to clinical circumstances:

- when seizures' frequency increased. This helps to determine
the need for dose adjustment before the drug is changed or a second
drug added.

- every 3 to 6 months to verify that blood concentration does
not drift out of the intended range.

Prognosis: The long-term prognosis of primary (or
idiopathic) epilepsy is fair. However, a small number of epileptic
dogs may become 'refractory' (high frequency of seizures despite high
serum level of anticonvulsant) to Phenobarbitone. Second epileptic
drug such as Bromide 30 mg/kg once daily can then be used as an
adjunct to Phenobarbitone.

Disclaimer: Any information contained on
this site relating to various medical, health, and fitness con-
ditions of Chihuahuas and their treatment is for informational
purposes only and is not meant to be a
substitute for the advice provided by your own veterinarian.
You should not use the information contained
herein for diagnosing the health of a Chihuahua - you should always
consult your own veterinarian.